Method of and means for locating leaks in a gas main or the like



F .1941 E. F. SCHULDT 55 METHOD OF AND MEANS .FOR LOCATING LEAKS IN AGAS MKIN OR THE LIKE Filed April 2, 1937 4 Sheets-Sheet 1 Feb. 27, 1940.E. F. SCHULDT METHOD OF AND MEANS FOR LOCATING LEAKS IN A GAS MAIN ORTHE LIKE Filed April 2. 1937 4 Sheets-Sheet 2 Feb. 27, 1940. E. F.SCHULDT METHOD OF AND MEANS FOR LOCATING LEAKS IN A GAS MAIN OR THE LIKEFiled April 2, 1937 4 Sheets-Sheet 5 Ira/19;? zon [Zmerf Scfzaldi.

Feb. 27, 1940. E. F. SCHULDT METHOD OF AND MEANS FOR LOCATING LEAKS IN AGAS MAIN OR THE LIKE Filed April 2, 1937 4 SheetsSheet 4 iii,

Patented Feb. 27, 1940 METHOD OF AND IWEANS FOR LOCATING LEAKS IN A GASMAIN OR THE LIKE Elmer F. Schuldt, Chicago, Ill.-

Application April 2, 1937, Serial No. 134,563

26 Claims.v (Cl. 13'7-77) This invention relates to a method of andmeans for locating leaks in gas mains, under ground fluid transmissionconduits and the like, and more particularly is directed to the locationof fluid leaks in low pressure distribution mains from within theconduit itself, to avoid the time, labor and expense of previously knownmethods of locatingsuch leaks.

The methods used heretofore with which I am familiar, in locating leaksin low pressure gas distribution systems and the like, have beenrelatively crude and uncertain. The sense of smell has been the mostimportant aid in locating the source of escaping gas. The judgment andexperience of the street foreman, and his familiarity with structures inthe street adjacent to the gas system, is next in importance. Bar-holes,made by driving a crowbar or the like through the ground to the conduit,are used to advantage, but their value is limited by the type of soil inwhich the main is laid. Porous soil, such as cinders or the like, willform a gas reservoir under pavement which may extend for more than onehundred feet away from the point at which gas is escaping. Wet clay soilsometimes gives no.

indication of a leak, even though the bar-holes are driven within a fewinches thereof. Barholes cannot be readily made when there is frost inthe ground. Y

The gas indicator has been used to excellent advantage to indicate gasconcentrations. Barholes, pavement cracks, sewers, duct lines, vaultsand the like in the vicinity of the gas leak are tested with theindicator. The street opening is made where gas of the highestconcentration is found. However, in porous soils, gas may be found inbar-holes extending many feet away from the actual point of leakage. I

The gas stethoscope is probably one of the greatest aids developed inrecent years for 10- eating service leaks, and aids in locating mainleaks between adjacent services. The value of the stethoscope dependslargely upon the judgment and experience of the operator, as his carmust be trained to remember and distinguish the various sounds andeliminate those sounds other than gas leak sounds. The instrument hasbeen used with some degree of success in situations where noises arelimited, such as an outlying district as distinguished from congesteddistricts.

Use has been made of all of the above mentioned methods in locatingleaks, and after a thorough survey, a street opening is made at the mostlikely spot. Many times the first opening is successfully chosen, andthe gas leak is found in the opening.

However, it quite often happens that the first opening is not'where theleak is located, and although location of the leak can sometimes bedetermined by tunneling each way along the main,

the limits of a tunneling operamay be necessary to locate a leak.

These street openings are wasteful and expensive, and consume much timeand labor, especially during colder weather.

Time is also an important element in the location of street leaks. Whenit takes more than one or two street openings to locate and repair a.leak, it naturally takes longer to eliminate the potential hazard. Thismay be serious when gas is leaking into a building, a sewer, or anunderground vault. Present methods have not proved adequate for thelocation of leaks with a minimum of expense and time.

It has been considered to locate gas leaks from the inside of the side.

main rather than from the out- The use of a small anemometer has beenconsidered, this being used by stopping the flow of gas in the main fromone direction, and any flow to the leak must therefore come from theother direction.

By pushing the anemometer through the main to a point just beyond theleak, the flow of. gas should be able to actuate the anemometer to givean indication. .l-lowever, while this device might be used to locate anunusually large leak in a small main, it is necessarily a delicatelybalanced instrument, which is difficult to manipulate through a. main,and for low pressure leaks has not been of any considerablev value.

Another attempted solution of this problem was the use of a smallmicrophone pushed along inside the main and employing the principle ofthe stethoscope.

Vibrations set up by the gas leak would be caught by. the microphone andtransmitted to suitable amplifying means where the intensity could be.determined with an indicating meter.

Preliminary experiments indicated that it was impossible todifferentiate between the sounds caused by a leak of the same magnitudeanywhere along a test pipe of some 25 feet in length.

As another attempted solution of this problem, a long rubber bag couldbe inserted into the main and inflated and deflated in successivesections of the main. When the bag was located where the leak wasoccurring, it would seal 01f the leak and surface indications thereofwould stop. However, in some cases, it is necessary to keep the sectionbagged off for an hour or more in order to be sure that the leak is inthe section isolated, because the ground under the pavement sometimesmakes an excellent reservoir or pocket for the gas, and the odorpersists long after the leak is blocked off. Such a method therefore isnot desirable, because of the time element involved, and otherdisadvantages which have arisen in practical use.

The present invention contemplates an improved method of and means forlocating leaks in low pressure transmission mains by employing theprinciple of locating the point at which a pressure drop in the mainoccurs. The location of such a pressure drop would indicate that thereis a leakage of gas from an opening in the main at the point at whichthe pressure drop occurs. However, the fact that most leaks are slightin rate of flow as compared with the large volume of gas alwaysavailable would ordinarily render it diflicult to measure this pressuredrop' correctly. It is therefore an object of the present invention toprovide means for interrupting the supply of gas to the section of mainbeing" tested, so that the pressure drop can be easily measured, becauseit would be of an appreciable value as compared to the static pressurein the main.

In carrying out the present invention, an opening is made in the main asclosely adjacent the of the bags from conduit means extending.

through the opening. The bags are then inflated and, by suitable meanslocated between the bags,

the pressure between the bags is determined upon suitable gauge meansdisposed at or adjacent the opening. If no appreciable pressure dropoccurs in the section of the main under test, the bags are deflated,moved to a next succeeding position slightly overlapping the previousposition, and again inflated. By successively moving the bags along theinterior of the main and stopping 01f flow between the bags whiletesting the pressure therebetween, the location of the leak can bereadily determined by the indication of the pressure gauge. Tests withthis apparatus provide a definite indication on the differential gaugewith a leakage as low as cu. ft. per hour. With larger leakages,differentials approaching .the main pressure were obtained. By the useof this method, in which the means which carries the bags and permitsinflation thereof is also provided with suitable length indicating meansfor determining the position of the bags with respect to the opening,the sections of the main extending in both directions away from theopening can be successively tested until the point at which the leak islocated has been determined. After the leak has once been located, theapparatus can be shifted in smaller increments of movement until theexact position of the leak is located, after which a street opening canbe made and the leak repaired. Thus, at the most, only two streetopenings are required in order to provide for definite location andrepair of gas leaks in distribution systems of this type.

In tests, theapparatus was used and successtions of the mains isobtained, which greatly re-' duces the time required for locating andrepairing the leak.

Still another feature of the present invention is the provision ofapparatus which is simple in design and assembly, economical inmanufacture, and which can be easily set up in operation by any streetforeman or similar employee.

The present invention also contemplates themethod of locating gas leakswhere the leak is which has heretofore been extremely difficult withprevious types of testing and locating apparatus.

Other objects and advantages of the present in-. vention will appearmore fully from the following detailed description which, taken inconjunction with the accompanying drawings, will disclose to thoseskilled in the art the particular construction and operation of apreferred form of the present invention.

In the drawings:

Figure 1 is a diagrammatic view showing one manner in which a test on agas main is accomplished by means of the present invention;

Figure 2 is a view diagrammatically illustrat ing the control panel andthe testing apparatus in position within a main;

Figure 3 is a detail view of the connections at the control panel;

Figure 4 is a View, partly in section, showing the connection from thepanel to the apparatus to be disposed within the main;

Figure 5 is a sectional view through the flexible conduit member takensubstantially on line 5-5 of Figure 4;

Figure 6 is a sectional view of the connection" to the first gas mainbag;

Figure '7 is a sectional view taken substantially on line 1-! of Figure6;

Figure v8 is a sectional view through the connection from the forwardend of the first gas bag to the conduit extending between the bags;

Figure 9 is a sectional view taken substantially on line 99 of Figure 8;

Figure 10 is a View, partly in elevation, of

the forward gas bag connection;

Figure 11 is a sectional view taken substantially on line II--H ofFigure 10;

Figure 12 is a sectional view taken substantially on line l2l2 of Figure11;

Figure 13 is a sectional view taken substantially on line I3-l3 ofFigure 11; and

Figure 14is a view showing a guiding member for the forward end of thetesting apparatus.

Referring now in detail to the drawings, and more particularly toFigures 2 to 14, inclusive, I have provided a control panel indicatedgenerally at 5, which panel is preferably mounted ina housing in suchmanner as to be inclined for facilitating reading of the same when it isset on the street or in a similar location adjacent the point at whichthe test is being made. This panel is provided with a'pressure gauge6,which gauge is provided for indicating the pressure within the bagslocated within the gas main, and is also providedwith a pressureconnection 'I to which may be attached any suitable type of pump or thelike for producing a pressure within the system. A suitable exhaustvalve 8 is also provided on the forward edge of the panel, for releasingthe pressure within, the apparatus, the valve 8 being provided withsuitable means whereby an exhauster may be attached thereto if it isdesired to provide some means of rapidly exhausting the fluid withinthe'system.

On the opposite side of the inlet 1 from the exhaust valveB, Ipreferably provide a connection indicated generally at 9, to which isattached the conduit for conducting the fluid under pressure from thecontrol panel through the gas main opening and into the bags disposed inthe opening.

Considering now in detail Figure 3, it will be noted that the pressuregauge 6 is provided with an'extension ll) whereby it maybe connected tothe T member I2, which T member is provided with oppositely extendingfittings l3 and M, and is also provided with the tapped pressure inletconnection 1, this preferably being in the form of a valve stem or thelike to which a pump may be connected in any suitable manner, From thefitting I 3, a conduitis extended, as indicated at E5, leading to theexhaust Valve 3, which valve is provided with a manually operable valveplug it, whereby it maybe closed,'or may be opened to allow exhaust ofpressure through the outlet ll. From the opposite fitting l4, aconduiti3 is extended into the bushing connecting member 9, which is mounted onthe control panel as indicated in Figure 2, this bushing 3 also beingprovided with a second conduit 19 leading into the coupling indicatedgenerallyat 23, which connects through the cap member. 22 to theinterior of a tank 23 adapted to contain alcohol or a similar indicatingfluid. The tank 23 is provided with a conduit 26, which extends down toa point adjacent the lower end thereof and is suitably sealed to the capmember 22, as indicated at 25.

he conduit 24 is connected through the member 32%; to an angularlyextending glass tube 21 which is supported in an inclined position onthe control panel 5, as indicated in Figure 2, and has its' outer endbent upwardly, as indicated at 28. A suitably graduated scale 29 isprovided on the panel 5, whereby the level of the fluid within the tube21 is indicated on the scale,andthe relative drop or rise in this levelcan readily be determined by means of the graduations on the scale. Itwill thus be apparent "that the effective pressure in the conduitl9-will cause a corresponding pressure on the surface of the liquid inthe tank 23, and consequently produce a certain head of liquid in themember 26 and tube 21, which level will vary with the pressure in theconduit It to give an indication in the testing of a gas main for leaks'Considering now Figure 2 in further detail, a gas main is indicatedgenerally at 3B, and at a suitable point in the main, which can bedetermined by the skill and experience of the operator, an opening ismade as indicated at 32,

through which opening a flexible conduit member formed of molded rubberor the like, indicated at 33, may be extended. This conduit 33- iscontions on the tape 31.

nected at its far end with a first gas bag member 34, and thencethroughthe spacing conduit 35 to the forward gasbag member 36. Preferably asteel tape 31 is secured to the rear end of the first gas bag member 34,and is suitably graduated so that upon pushing of the tape the bags 34and 36' are moved longitudinally along the interior of the main adistance determined by the gradua- The connection 35 between the twobags is sufliciently rigid to maintain the spacing approximately thesame throughout the movement of the bags.

In Figure 4 I have illustrated in detail one manner in which the conduit33 may be connected to the conduits l8 and I9 and the bushing 9. As willbe noted, the conduit 33, which is preferably formed of molded rubber orthe like, is provided with spaced tubes therein, indicated at 33 and 39,which preferably in the form of copper or similar flexible tubes, which"are embedded in the rubber of the member 33 and project from one endthereof, as shown in detail in Figure l. The tubes 38 and 39 preferablyextend into a suitable connection member 40, having a flange 42 at oneend thereof which is engaged within the flanged end 43 of a wing nut 44.The wing nut M is threaded over bushing 9 to bring the ends of the tubes38 and 39 into cooperative rela-' tionship, through the passageways 45and 46, with the ends of the conduits l8 and I9 carried by the bushing9. Suitable gasket means M is preferably provided for sealing theconnection between the members and 9, to prevent any leakage of fluidaround the openings and 46 between the two members. The conduit 33extends from, the con-, trol panel connection provided by the wing nut44, and throughout the major portion of its length is provided with themolded recesses &8 and 39 communicating, respectively, at the controlpanel end of the tubing with'the tubes 38 and 39, and at the oppositeend having communication with a pair of tubes 53 and 52 carried by a,coupling member 53 corresponding somewhat to the member 40 of Figure 4,having a flanged, end 54 engaged by the flanged end of the coupling nut55. I

The member 53 is alsoprovided with a pair of spaced openings adapted toreceive the screw members 53 for securing the steel tape 3'! to themember 53, as shown in detail in Figure '7, whereby the tape is rigidlysecured to the coupling member and extends longitudinally alongside theconduit 33. I

The coupling nut is threaded over a bushing member 5&5, there beingsuitable gasket means 33 disposed. between the end of the bushing andthe flanged'end 5d of the member The tubes 55) and 52 extend intosuitable recesses in the bushing member, and the tube 53 is adapted tohave communication through the bushing memher with a tube Gil extendingthrough the sleeve this sleeve being provided with a transversepartition member (33 preferably formed of spring material and extendinginto the gas bag 34 beyond the sleeve member 62. The sleeve member 62opens into the bushing 53 in communication with the tube 52, wherebyfluid under pressure passing from the conduit it through the bushing 9and through the tube 38 and passageway 138 to the tube 52 enters theinterior of the bag 34 and produces inflation thereof to the form shownin Figure 2. The tube 33 is provided, adjacent its opposite end, with aflexible conduit member M which may be cemented thereto,

the member is connecting with atube 35 as" shown in Figure 8, leadingoutwardly through the sleeve member 66 as indicated at 61 to a pointintermediate the bags 34 and 36, such as indicated in Figure 2. Thesleeve member 66 is provided with an open passageway which communicateson opposite sides of the spring member 63 with the interior of acoupling member 68 threaded over the outer end of the sleeve 66 andforming a continuation thereof. The Coupling member 68 is also providedwith a resilient steel spring member or the like, indicated at ill,which may be either a fiat spring member or may be a helically coiledspring member, as desired, which extends within the conduit and iscemented over a reduced portion 12 of the member 68. Fluid underpressure from the interior of the bag 34 therefore passes through theport 13 of thesleeve member 66 and through the coupling member 68 intothe interior of the conduit 35, which is preferably a flexible conduitsuch as reinforced rubber tubing or the like.

At its opposite end, the tubing 35 is secured to the reduced portion Mof a coupling member 75 threaded to the outer end of a sleeve 16 towhich the bag 3% is connected. The member 10 is preferably spot weldedor otherwise secured to the interior of the coupling member 15, andtherefore forms a resilient connection between the coupling members 68and "I5. Fluid under pressure therefore enters the interior of the bag36 to inflate the same. The sleeve member 16 is also provided with aresilient spring member 11, welded or otherwise suitably secured theretoas indicated at E8, which extends through the bag 36 and is secured atits opposite end to the interior of the end member 19 to which the0pposite end of the bag 36 is secured.

The member i9 closes off the forward end of the bag 36, so that nofurther transmission of fluid outwardly from the bag 35 is possible.

At its outer end, the member 19 is recessed as indicated at St, toreceive the reduced end 82 of a guide supporting member 83. The member83 has a groove 84 formed in its reduced end, which is clamped inposition by the transverse pin 85 extending through the member 19. Thisallows the member 83 to rotate with respect to the member 19, butprevents any relative longitudinal movement therebetween. Secured to theforward end of the member 83 is a resilient arm member 36, which entersinto a slotted portion in the end of the member 83 and is securedtherein by means of rivet members 31. The arm 85, at its forward end, isprovided with a suitable pivot pin 87 upon which two oppositely disposedsemi-spherical roller members 88 are mounted for free rotation. By theprovision of this guiding member, as the testing assembly is pushedthrough the gas main, the rollers 88 will guide the same around bends orthe like in a gas main, especially when an offset is provided to clear avault or underground manhole, in which case the apparatus must be guidedthrough elbows and by the provision of the rollers 88, this can beaccomplished without any substantial buckling or distortion of theassembly.

The gas bags 36 and 34 are preferably made of a material such as rubberor the like, which may be treated to provide a wear-resisting surface,and which, at opposite ends, are provided with projecting nippleportions indicated gen erally at 90. These nipple portions are suitablycemented to the external surfaces of the respective sleeve members 62,66, 16 and I9, and if desired, in order to assist in retaining thenipples in sealing contact with the external surfaces of the sleeves, toprevent airleaking therepast, suitable clamping rings 92 may be providedencircling the nipples 9! and holding the same firmly against the,external periphery of the sleeve.

In the operation of the structure thus far described, the system isinserted through the opening 32 in the gas main in a deflated condition,that is, with the bags 34 and 3G deflated. It is initially set up withthe bag 3 adjacent the opening 32, and the bags, are then inflated byapplying a pump or the like to the pressure inlet l and developing apressure in the system which will be indicated by the gauge 6. Thisfluid under pressure is transmitted to conduit I8 extending from the Tfitting l2 andthrough I the tube 38 and conduit i8 of the flexibletubing 33 to the interior of the first bag 34 through the sleeve 62.This bag is thereupon inflated, and the remaining pressure transmittedthrough the conduit 35 into the interior of the bag 36 through thesleeve 16. The bagsare preferably inflated to a pressure ofapproximately 6 lbs. as indicated on the gauge t, the normal gaspressure within the main being tested being of the order of /4 lb. persquare inch. Upon inflation of the bags, if there'is any leak betweenthe two bags 34 and SEiQthe port 6')! ofthe tube 65 will indicate adecrease in pressure between the bags, this decrease in pressure beingtransmitted through the conduits 6d and the tube to the tubing 33, andfrom this tubing through the conduit i9 to the tank 23. A decrease ofpressure will result in falling of the liquid level in the tube 21, asindicated upon the scale 29,

and the rate of fall of this liquid will determine the quantitativeamount of gas issuing from the leak. With the apparatus as thusoperated, a leak of cu. ftpper hour has been indicated upon the gauge2?. If there is no leakbetween the bags 3 3 and '36, indicating no leakin that section of the main, there will be no decrease of pressure,sensed by the apparatus, and consequently the level of thefluid in thetube 21 will remain stationary.-

Preferably the bags 34 and 3B are spaced apart a distance ofapproximately 9 ft. bythe conduit 35 and the steel spring member ill.The'tape 3'! may be graduated in any .suitable manner, and preferablythe bags are successively moved along the line in steps of approximately8 feet, to insure that there will be an overlapping of the respectivepositions of the bags, in order to insure the detection of any leakapproximately at the point where the bags may be located.

If no drop of pressure in the main between the bags is sensed after theinitial set-up, the pressure is released by opening the valve 8,'and thebags then deflated and moved further along the main by the tape 31 to apoint in which the rear bag occupies a position slightly behind theinitial position of the forward bag. The'bags are leak, the exactposition of the leak with respect to the opening 2-32 can be determinedby the graduations on the tape 31. It is then only necessary to dig downto the main at this point and to repair the leak. It is to beunderstood, of course, that when the assembly is inserted through theopening 32 and inflated in position, soap or the like, as indicated at95%, is applied about the opening to prevent the escape of gastherepast. The bags preferably are maintained in position during therepair of the leak to prevent any fur ther leakage of gas. The spacedbags may also be used to determine the condition of a-main independentlyof location of leaks, and can be used to shut off sections of a main incase of fire at a service where the shut-off valves are inacat anydistance from the initial opening 32. Furresponding to a building lot,in which the test I ther, by means of the guiding member indicated inFigure 14, the apparatus can be successfully pushed around offsets orelbow turns in the main.

is being conducted. After this section of the main has been tested theservice can be again connected, and the next service connection can beclosed off for testing of the main adjacent that service connection.

If the apparatus indicates a leak at the service connection, it is ofcourse necessary to then test the service connection itself, sinceobviously the leak is not in the distribution main proper.

By the present system it is t erefore possible to locate gas leakswithout the necessity of making more two openings in the street orpavement, and it is also possible to locate preciscly the point at whichthe gas is escaping prior to making the second opening, so that theopencan be made at the point which will to the greatest extentfacilitate repair of the leak.

It sometimes'happens that a distribution system is laid out in whichcertain of the mains are dead-ended, that is, are not connected so thatgas may be fed from both ends thereof to the intermediate section. Sucha system is illustrated in Figure l, inv which the main ltd isprovidedwith the dead-cud or closure cap 262. In such a main, in orderto make an accurate test for gas leaks, it becomes necessary to providea by-pass line W3, whereby gas posterior to the testing apparatus may .etransmitted through the line we to a point anterior to the testingapparatus, so that the gas pressure upon the outer surfaces of the 3 1can be maintained, whereby the wi shut off flow of gas from both. endsof the toward the 1E&k,'811d vdll thereby pro-- duce an indication ofthe leak the point marked X. However, this is a specific type of test,and in the ordinary distribution main, which is fed from bothdirections, no such by passing arrangement need be provided. I

It is therefore believed that the present invention possesses distinctadvantages in the reduction of time and labor necessary for locating andrepairing leaks in gas mains of distribution systems and the like.Further, the present apparatus allows for'the location of such leakswith out making a number of openings in the pavement or the soilstructure above the main.

It is, ofcourse, possible to use means other than inflatable gas mainbags for interrupting the supply of gas to the'section of main undertest, such as mechanically actuated expansible members or the like.

I am aware that various other changes may be made in the details ofconstruction in the illustrated embodiment of the invention, andtherefore do not intend to be limited except as deflnedby the scope andspirit. of the appended claims.

I claim: 1

l. The method of locating a leakin a gas dispoint any variations in thestatic pressure caused by leakage from within the particular section atwhich said condition has been established.

2. The method of locating a leak in a fluid transmission main, whichcomprises successively internally blocking ofi sections of the mainagainst fluid flow thereinto, and indicating externally of the main thefluid pressure conditions in the section of main so blocked off.

3. The method of locating a leak in a fluid transmission conduit, whichcomprises internally blocking oil a predetermined length of said conduitagainst fluid flow thereinto, continuously indicating the fluid pressurein said length, and successively blocking off overlapped lengths of saidconduit to determine the particular length in which the pressuredecreases when so blocked oil.

4. The method of locating a leak in a fluid transmission conduit, whichcomprises successively internally blocking off fluid flow intopredetermined lengths of said conduit from a given reference point,continuously indicating the fluid pressure conditions in the lengthsblocked off to determine the particular length in which the pressuredecreases, and continuously indicating the distance from said referencepoint to the length under test.

5. The method of locating a leak in a fluid transmission conduit havingfluid continuously flowing therethrough, which comprises testingsuccessively predetermined lengths of said conduit by internallyblocking off fluid flowto the length under test, and determining anyleakage in the length under test by sensing the variation in pressure inthe said length.

6. The method of locating a leak in a fluid transmission conduit havinga substantially pre determined fluid pressure therein, which cornuniformsteps from said point for variations in.

static pressure in the section under test, and simultaneously indicatingthe distance from said point to the section under test.

8. The method of testing a section of a gas main for leakage, whichcomprises blocking said section at two spaced apart points to shut offgas flow through said section while trapping gas therein between saidtwo spaced apart points, measuring variations in static pressure of thetrapped gas, and measuringthe distance from said section to an exteriorremote point.

9. Apparatus for locating a leak in a gas distribution main comprising apair of expansible members spaced apart a predetermined distance andmovable as a unit axially through said main from a given referencepoint, means connected to said members and operable from adjacent saidpoint for expanding said members to shut off gas flow into the's'ectionof the main therebetween, a gauge located adjacent said point and havinga pressure connection opening into said main section intermediate saidmembers for indicating variations in static pressure in said section,and means for measuring the distance from said reference point to saidpair of expansible members. v

10. Apparatus for locating a leak in a gas distribution main comprisinga pair'of expansible members spaced apart a predetermined distance andmovable as a unit axially through said main from a given referencepoint, means connected to said members and operable from adjacent saidpoint for expanding said members to shut off gas flow into the sectionof the main therebetween, a gauge located adjacent said point and havinga pressure connection opening into said main section intermediate saidmembers for indicating variations in static pressure in said section,and means operable from said point for moving said members axiallythrough said main.

11. Apparatus for locating a leak in a gas distribution main comprisinga pair of expansible members spaced apart a predetermined distance andmovable as a unit axially through said main from a given referencepoint, means connected to said members and operable from adjacent saidpoint for expanding said members to shut ofi gas flow into the sectionof the main there between, a gauge located adjacent said point andhaving a pressure connection opening into said main section intermediatesaid members for indicating variations in static pressure in said section, and means operable from said point for moving said members axiallythrough said main,

'said means having indicia thereon for indicating the position ofsaidmembers relative to said point.' 1

12. Means for locating a gas leak in a distribution main, comprising apair of expansible members interconnected in predetermined space ing andmovable as a unit axially of said main, means for expanding said membersto prevent gas flow therebetween, including flexible means fortransmitting the expanding force to said members from'a remotepoint, apressure connection carried by said last named means and openintermediate said members, means at said point responsive to'pressure insaid connection for indicating the pressure in the main intermediatesaid inemberspand means for moving said members axially of said main andsimultaneously indicating the position of said members with respect tosaid point. r 13. Apparatus for locating a leak in a gas distributionmain, comprising a control panel, a pair of inflatable members adaptedto be inserted in deflated condition through a relatively small openingin the main and having a relatively stiff pressure-transmittingconnection therebetween of predetermined length, a flexiblepressure-transmitting conduit between said members and said panel havingtwo passageways therein, means at said panel for supplying fluid underpressure through one of said passageways to inflate both said membersfor stopping oil gas flow in said main between said members, said otherpassageway being open to the interior of said main between said members,gauge means at said panel connected to said other passagee way andresponsive to the pressure in said main between said members, and meansfor moving said members axially along said main from said opening andincluding means indicating the position of said members relative to saidopening.

14. In apparatus for locating a leak in a gas distribution main, a unitfor stopping 01f flow of gas to a section of main under test, comprisinga pair of inflatable members adapted to be inserted into the main indeflated condition, a resilient inextensible spacing means between saidmembers and extending at one end through the rear member, a flexiblepressure-transmitting conduit connected to the rear member, a secondflexible pressure-transmitting conduit enclosing said spacing means andcommunicating with the interior of both said members for equalizing thepressure therebetween, means secured to the extended end of saidresilient inextensible spacing means, whereby said unit can be movedaxially within said main and said members can be inflated and deflatedfrom a point externally of said main, and a pressure inextensiblepropelling connection extending into the space between said andcommunicating with the interior of both said members for equalizing thepressure therebetween, and a fluid pressure connection extending throughsaid first flexible conduit and through said rear member and openinginto the main intermediate said members whereby variations in staticpressure in said section of said main can be indicated externally ofsaid main.

16. In apparatus for locating a leak in a gas distribution main, meansfor successively testing predetermined sections of said main, comprisinga pair of expansible members spaced apart a predetermined distance andhaving means extending outwardly of said main at a given reference pointfor moving said members axially within said main and for expanding saidmembers to shut oii flow of gas to the section of the main between saidmembers, and means for indicating the distance from the section undertest to said reference point. e

17.1n apparatus for locating a leak in a gas distribution main, meansfor successively testing predetermined sectionsof said main, comprisinga pair of expansible members spaced apart a predetermined distance andhaving means extending outwardly of said main at a given reference pointfor moving said members axially within said main and for expanding saidmembers to shut off flow of gas to the section of the main between saidmembers, and means opening into said main intermediate said members andextending through said expanding means for indicating externally of saidmain at said reference point variations in static pressure in said mainsection between said members.

18. A method of locating leaks in a fluid transmission main, whichcomprises making an opening in the main at a point adjacent the leak,inserting interconnected spaced fluid blocking means into the mainthrough the opening, continuously registering the fluid pressure in thesection of main between said blocking means, and moving said means intosuccessive. overlapping positions along the main until the pressureregistration indicates a continuous decrease in pressure in the sectionof main between said blocking means.

19. The method of locating a leak in a gas distribution conduit, whichcomprises interrupting the supply of gas to the section of main undertest, measuring the pressure drop in the section to which the supply hasbeen interrupted, and measuring the distance from a reference point tothe section in Which a pressure drop has been ascertained.

20. The method of locating a leak in a gas distribution conduit, whichcomprises interrupting the supply of gas to successive overlappingsections of main, and successively measuring the rate of pressure dropin each section after the gas supply thereto has been interrupted.

21. The combination, with apparatus of the class described for locatinga leak in a gas distribution main, of means for interrupting the flow ofgas into a selected section of said main, comprising a pair ofinflatable bags, each of said bags having a nipple at opposite endsthereof, a flexible conduit connecting adjacent nipples of each bag,resilient spacing means within said conduit, a closure for the oppositenipple of one of said bags, and a pair of pressure connections,

one extending to the opposite nipple of the other of said bags and theother extending through said other bag and into communication with thespace between said bags.

22. The method of determining the condition of successive sections of agas distribution main having gas flowing therethrough, which comprisessuccessively interrupting the supply of gas to said sections, andmeasuring the pressure conditions in the section under test. 4

23. The method of determining the condition of successive sections of agas distribution main having gas flowing therethrough, which comprisessuccessively interrupting the sup-ply of gas to said sections, slightlydecreasing the volume in the section under test, and indicating anyvariations in static pressure in said section.

24. Apparatus for locating a leak in a gas distribution means comprisinga pair of inflatable bags, a tubular member connecting said bags,whereby the interior of one bag is in communication with the interior ofthe other, a conduit connected at one end to one of said bags and havingtwo generally longitudinally extending horses formed therein, a tubularconnection leading from one of said bores into communication with theinterior of said bags, a second tubular connection leading from theother bore to said one bag and into the space between said bags, andpressure measuring means connected to said conduit in communication withsaid second bore.

25; Apparatus for locating a leak in a gas distribution main, comprisinga pair of inflatable bags, each having a resilient inextensible memberconnecting the ends thereof, a tubular member connecting said bags andproviding for communication from the'interior of one bag to the interiorof the other, a resilient inextensible member disposed within saidtubular connection and connected at its opposite ends to theinextensible members in said bags, a conduit having generally parallellongitudinally disposed bores therein and connected at one end to theouter end of one of said bags and the outer end of the inextensiblemember associated therewith, a tubular connection from one of said boresto the interior of said bags, a second tubular connection from the otherof said bores to the space between said bags, said second connectionincluding a flexible section and extending generally along theinextensib-le member in said one bag, and pressure measuring meansassociated with said other bore.

26. Apparatus for locating a leak in a gas distribution main, comprisinga pair of inflatable bags, a tubular bushing secured at each end of eachof said bags, a resilient inextensible member disposed in each of saidbags and connected at each end to the associated bushing, a tubularmember connecting adjacent ends of said bags and including bushings atthe end thereof corinected to the bushings at the adjacent ends of saidbags, a resilient inextensible member disposed within said tubularmember and connected to the bushings at the outer ends of the latter, aconduit having generally parallel longitudinally disposed bores therein,a tubular connection from one of said bores leading through the adjacentbushing into the interior of said one bag, a second tubular connectionleading from the other bore through said one bag and outwardly throughthe bushing at the other end. thereof into communication with the spacebetween said bags, and pressure,

supplying and measuring means adapted to be connected, respectively,with the outer ends of said bores.

ELMER F. SCI-IUIDT.

CERTIFICATE OF CORRECTION. I Patent No. 2,192,155; February 27,19uo.

' ELMER SCHULDT.

It is hereby Certified that error appears in the printed Specificationof the above numbered patent requiring correction as follows: Page 7sec- 0nd column, line 6, claim 2h, for the word "horses read bores; andthat the said Letters Patent should be read with this orrection thereinthat the same may conform to the record of the case 'in the PatentOffice.

Signed and sealed this 2nd day of April, A. D. 19LLO.

Henry Van Arsdale, (Seal) Acting Comrhissioner ofPatents.

